The present invention relates to a new and improved system and method for converting digital multiple bit audio signals to analog audio signals and for generating internal or localized audio tone signals in a manner which is more economical in terms of necessary circuitry and hardware than heretofore possible. More particularly, the system of the present invention can be utilized to great advantage in a communication network of the type which has a bus for carrying a plurality of digital, multiple bit time divided channels of information including audio to be conveyed therefrom in analog form and data which controls the operation of the system and the overall operation of the network. The system and method of the present invention also provide for the generation of digitized data and placing the data onto the bus.
Communication networks wherein any one of a plurality of operator positions is to be coupled to any one of a plurality of remotely located base station transmitters often utilize time division multiplexing to provide the number of audio channels necessary for achieving total network capacity. In networks of this type, a bus is generally utilized for carrying a plurality of digital multiple bit time divided channels of audio which run in both directions between the operator positions and the base stations. An interface system is generally required between the bus and each of the base stations. The interface system must be capable of decoding the digitized audio received from the operator positions and converting the same to analog audio signals for transmission. The interface system must also be capable of generating tones for keying purposes or the like, and, depending on the overall system and network organization and operation, generating data.
In the prior art, each of the foregoing functions has been accomplished separately and independently. Hence, each interface system would have a separate decoder for only decoding digitized audio, a separate tone generator for generating audio tones, and a separate data generating means for placing required data onto the bus to maintain the proper network organization.
The separate implementation of these functions adversely impacts upon the overall network cost, especially when a number of interface systems are required. Both the cost of labor and materials is increased as a result of the separate and dedicated circuitry required to accomplish each of these separate functions.
Not only is network cost adversely affected, but the cost of maintaining the network is also adversely affected. When more component parts are required in a system, either the physical size of the system must be increased to accommodate all of the components, or the component density must be increased. If the physical size of the network is increased, the overhead associated with the space which the systems occupy also must increase. In the latter case, if component density is increased, the systems are rendered more complicated thus increasing service maintenance costs when service is required.
It is therefore a general object of the present invention to provide a new and improved system and method for converting digitized audio carried on a bus in one of a plurality of time slots to analog audio and for generating localized tone signals.
It is another object of the present invention to provide such a system and method which requires fewer component parts than heretofore required for accomplishing these functions.
It is a further object of the present invention to provide such a system and method which includes generating data and placing the data onto the bus in a manner which does not unduly increase the complexity of the system.
It is a still further object of the present invention to provide such a system wherein the analog tones and decoded analog audio are provided from a common decoder.